Synopsis

Important: kernel security and bug fix update

Type/Severity

Security Advisory: Important

Topic

An update for kernel is now available for Red Hat Enterprise Linux 6.5 Advanced Update Support.

Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fix(es):

• An integer overflow flaw was found in the way the Linux kernel's networking subsystem processed TCP Selective Acknowledgment (SACK) segments. While processing SACK segments, the Linux kernel's socket buffer (SKB) data structure becomes fragmented. Each fragment is about TCP maximum segment size (MSS) bytes. To efficiently process SACK blocks, the Linux kernel merges multiple fragmented SKBs into one, potentially overflowing the variable holding the number of segments. A remote attacker could use this flaw to crash the Linux kernel by sending a crafted sequence of SACK segments on a TCP connection with small value of TCP MSS, resulting in a denial of service (DoS). (CVE-2019-11477)
  
• kernel: Double free in lib/idr.c (CVE-2019-3896)
  
• Kernel: tcp: excessive resource consumption while processing SACK blocks allows remote denial of service (CVE-2019-11478)
  
• Kernel: tcp: excessive resource consumption for TCP connections with low MSS allows remote denial of service (CVE-2019-11479)
  

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Bug Fix(es):

• MDS mitigations not enabled on Intel Skylake CPUs (BZ#1713025)
  
• [RHEL6] md_clear flag missing from /proc/cpuinfo (BZ#1713028)
  
• RHEL6 kernel does not disable SMT with mds=full,nosmt (BZ#1713043)

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.

Affected Products

• Red Hat Enterprise Linux Server - AUS 6.5 x86_64

Fixes

• BZ - 1694812 - CVE-2019-3896 kernel: Double free in lib/idr.c
• BZ - 1719123 - CVE-2019-11477 Kernel: tcp: integer overflow while processing SACK blocks allows remote denial of service
• BZ - 1719128 - CVE-2019-11478 Kernel: tcp: excessive resource consumption while processing SACK blocks allows remote denial of service
• BZ - 1719129 - CVE-2019-11479 Kernel: tcp: excessive resource consumption for TCP connections with low MSS allows remote denial of service

CVEs

• CVE-2019-3896
• CVE-2019-11477
• CVE-2019-11478
• CVE-2019-11479

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/security/vulnerabilities/tcpsack

Red Hat Enterprise Linux Server - AUS 6.5

SRPM
kernel-2.6.32-431.95.3.el6.src.rpm	SHA-256: a1ef535f794f6a5c3ddb12346cfe2ae487a849db4ad58079187dca8fd34962f5
x86_64
kernel-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: b6b771e6bd3608b033c588c526b20190299d2dd84668420021bcffd59181241a
kernel-abi-whitelists-2.6.32-431.95.3.el6.noarch.rpm	SHA-256: b713a468fe9f7812e810cf095b72083a075e81692bf729ea1839c0978924bf07
kernel-debug-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 17901942be21fd0ab42a6682ef5f33903238ae34a6d147d8994dafe3f42a176e
kernel-debug-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: b6208377c1fe6398a76cf73983e0bd82bce1e106023959a85f5d94e182a3d049
kernel-debug-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: b6208377c1fe6398a76cf73983e0bd82bce1e106023959a85f5d94e182a3d049
kernel-debug-devel-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: d2f52422ebe57aa69e998de56e934ee34ab15f055680a83de5139126f1cdc2dc
kernel-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: b0f0ab5f881b39762cfcc90cfcbf7c9b15a789cb3adcdd0c6ae9fcbfad42ff64
kernel-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: b0f0ab5f881b39762cfcc90cfcbf7c9b15a789cb3adcdd0c6ae9fcbfad42ff64
kernel-debuginfo-common-x86_64-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 3577fa7a141635951bed551dc895dc90786a261acd141f39768889deed76ad94
kernel-debuginfo-common-x86_64-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 3577fa7a141635951bed551dc895dc90786a261acd141f39768889deed76ad94
kernel-devel-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 2f999793132b88b8550b16bb02ca240c355963543bc45dd27c7e15d0ba8d522c
kernel-doc-2.6.32-431.95.3.el6.noarch.rpm	SHA-256: 5a4c1541b242568b056580649c3fd45dc18452d97ee27e26dba8a316c992180c
kernel-firmware-2.6.32-431.95.3.el6.noarch.rpm	SHA-256: dfb3cd3ba4afec5586ad45cea5507c066e5de85fe37da9ea976d5654d39e7515
kernel-headers-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 2ed2d0d682d2de8b21ec03c43f20719a5ae08321dd6c6dfc16030eabfdfa69d2
perf-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: ddf2dac36248aa0495b539e645925afd1099cb5d6d26bb1fb8168010476ffa57
perf-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 36331097d7054f6ae30e52b55215aac43f6229632c0990b3f9a328082e614299
perf-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 36331097d7054f6ae30e52b55215aac43f6229632c0990b3f9a328082e614299
python-perf-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: d816dbf384f4f7e5a44da541e006efea917de9d67c01ea2c827353b037603ee3
python-perf-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 83ba61ebafd7f9c0f013bbe2b265cdfaca935b24e08420785025ac0c753b25b1
python-perf-debuginfo-2.6.32-431.95.3.el6.x86_64.rpm	SHA-256: 83ba61ebafd7f9c0f013bbe2b265cdfaca935b24e08420785025ac0c753b25b1